Articulated surgical instrument for performing minimally invasive surgery with enhanced dexterity and sensitivity

ABSTRACT

An articulated surgical instrument for enhancing the performance of minimally invasive surgical procedures. The instrument has a high degree of dexterity, low friction, low inertia and good force reflection. A unique cable and pulley drive system operates to reduce friction and enhance force reflection. A unique wrist mechanism operates to enhance surgical dexterity compared to standard laparoscopic instruments. The system is optimized to reduce the number of actuators required and thus produce a fully functional articulated surgical instrument of minimum size.

This application is a continuation of, and claims the benefit ofpriority from, U.S. patent application Ser. No. 11/243,730, filed Oct.4,2005 now U.S. Pat. No. 7,316,681, which is a continuation U.S. patentapplication Ser. No. 10/076,812, filed Feb. 15, 2002 (now U.S. Pat. No.6,991,627), which is a continuation of Ser. No. 09/340,946, filed Jun.28, 1999 (now U.S. Pat. No. 6,371,952), which is a continuation of U.S.patent application Ser. No. 09/030,661, filed Feb. 25, 1998 (now U.S.Pat. No. 5,976,122), which is a continuation of U.S. patent applicationSer. No. 08/857,776, filed May 16, 1997 (now U.S. Pat. No. 5,792,135),which claims priority to U.S. Provisional Application No. 60/017,981,filed May 20, 1996, the full disclosures of which are incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates generally to methods and apparatus for enhancingthe performance of minimally invasive surgery. This invention relatesparticularly to surgical instruments that augment a surgeon's ability toperform minimally invasive surgical procedures. This invention relatesmore particularly to a novel articulated surgical instrument forminimally invasive surgery which provides a high degree of dexterity,low friction, low inertia and good force reflection.

BACKGROUND OF THE INVENTION

Minimally invasive medical techniques are aimed at reducing the amountof extraneous tissue which must be damaged during diagnostic or surgicalprocedures, thereby reducing patient recovery time, discomfort, anddeleterious side effects. Approximately 21,000,000 surgeries are nowperformed each year in the United States. It is estimated that 8,000,000of these surgeries can potentially be performed in a minimally invasivemanner. However, only about 1,000,000 surgeries currently use thesetechniques due to limitations in minimally invasive surgical instrumentsand techniques and the additional surgical training required to masterthem.

Advances in minimally invasive surgical technology could have a dramaticimpact. The average length of a hospital stay for a standard surgery is8 days, while the average length for the equivalent minimally invasivesurgery is 4 days. Thus, the complete adoption of minimally invasivetechniques could save 28,000,000 hospital days, and billions of dollarsannually in hospital residency costs alone. Patient recovery times,patient discomfort, surgical side effects, and time away from work arealso reduced with minimally invasive surgery.

The most common form of minimally invasive surgery is endoscopy.Probably the most common form of endoscopy is laparoscopy which isminimally-invasive inspection and surgery inside the abdominal cavity.In standard laparoscopic surgery, a patient's abdomen is insufflatedwith gas, and cannula sleeves are passed through small (approximately ½inch) incisions to provide entry ports for laparoscopic surgicalinstruments.

The laparoscopic surgical instruments generally include a laparoscopefor viewing the surgical field, and working tools such as clamps,graspers, scissors, staplers, and needle holders. The working tools aresimilar to those used in conventional (open) surgery, except that theworking end of each tool is separated from its handle by anapproximately 12-inch long extension tube.

To perform surgical procedures, the surgeon passes instruments throughthe cannula and manipulates them inside the abdomen by sliding them inand out through the cannula, rotating them in the cannula, levering(i.e., pivoting) the instruments in the abdominal wall and actuating endeffectors on the distal end of the instruments. The instruments pivotaround centers of rotation approximately defined by the incisions in themuscles of the abdominal wall. The surgeon monitors the procedure bymeans of a television monitor which displays the abdominal worksiteimage provided by the laparoscopic camera.

Similar endoscopic techniques are employed in arthroscopy,retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy,sinoscopy, hysteroscopy and urethroscopy. The common feature of all ofthese minimally invasive surgical techniques is that they visualize aworksite within the human body and pass specially designed surgicalinstruments through natural orifices or small incisions to the worksiteto manipulate human tissues and organs thus avoiding the collateraltrauma caused to surrounding tissues which would result from creatingopen surgical access.

There are many disadvantages of current minimally invasive surgicaltechnology. For example, existing MIS instruments deny the surgeon theflexibility of tool placement found in open surgery. Most laparoscopictools have rigid shafts and are constrained to approach the worksitefrom the direction of the small incision. Additionally, the length andconstruction of many endoscopic instruments reduces the surgeon'sability to feel forces exerted by tissues and organs on the end effectorof the tool. The lack of dexterity and sensitivity provided byendoscopic tools is a major impediment to the expansion of minimallyinvasive surgery.

Telesurgery systems for use in surgery are being developed to increase asurgeon's dexterity as well as to allow a surgeon to operate on apatient from a remote location. Telesurgery is a general term forsurgical systems where the surgeon uses some form of servomechanism tomanipulate the surgical instruments movements rather than directlyholding and moving the tools. In a system for telesurgery, the surgeonis provided with an image of the patient's body at the remote location.While viewing the three-dimensional image, the surgeon performs thesurgical procedures on the patient by manipulating a master device whichcontrols the motion of a servomechanism-actuated instrument. Thesurgeon's hands and the master device are positioned relative to theimage of the operation site in the same orientation as the instrument ispositioned relative to the act. During the operation, the instrumentprovides mechanical actuation and control of a variety of surgicalinstruments, such as tissue graspers, needle drivers, etc., that eachperform various functions for the surgeon, i.e., holding or driving aneedle, grasping a blood vessel or dissecting tissue.

Such telesurgery systems have been proposed for both open and endoscopicprocedures. An overview of the state of the art with respect totelesurgery technology can be found in “Computer Integrated Surgery:Technology And Clinical Applications” (MIT Press, 1996). Moreover, priorsystems for telesurgery are described in U.S. Pat. Nos. 5,417,210,5,402,801, 5,397,323, 5,445,166, 5,279,309, 5,299,288.

However methods of performing telesurgery using telemanipulators stillrequire the development of dexterous surgical instruments capable oftransmitting position, force, and tactile sensations from the surgicalinstrument back to the surgeon's hands as he/she operates thetelesurgery system such that the system the surgeon has the same feelingas if manipulating the surgical instruments directly by hand. A system'sability to provide force reflection is limited by factors such asfriction within the mechanisms, gravity, the inertia of the surgicalinstrument and forces exerted on the instrument at the surgicalincision.

What is needed, therefore, is a surgical instrument that increases thedexterity with which a surgeon can perform minimally invasive surgicalprocedures.

It would also be desirable to provide a dexterous surgical apparatushaving a wrist with two degrees-of-freedom.

It would further be desirable to provide a wrist mechanism that has lowfriction in order to provide the surgeon with sensitive feedback offorces exerted on the surgical instrument.

It would still further be desirable to provide a surgical instrumenthaving a wrist mechanism for minimally invasive surgery which issuitable for operation in a telemanipulator mechanism.

SUMMARY AND OBJECTS OF THE INVENTION

Accordingly, it is an object of this invention to provide a surgicalinstrument that increases the dexterity with which a surgeon can performminimally invasive surgical procedures.

It is also an object of this invention to provide a dexterous surgicalapparatus having a wrist with two degrees-of-freedom.

It is a further object of this invention to provide a wrist mechanismthat has low friction in order to provide the surgeon with sensitivefeedback of forces exerted on the surgical instrument.

It is a still further object of this invention to provide a surgicalinstrument having a wrist mechanism for minimally invasive surgery whichis suitable for, operation in a telemanipulator mechanism.

In accordance with the above objects of the invention applicantsdescribe a compact articulated surgical instrument suitable forendoscopic surgery. The instrument has two opposed pivoting jaws and apivoting wrist member. The instrument is capable of providing forcereflection with high sensitivity. The instrument is adapted to becoupled via a servomechanism to a master control operated by a surgeon.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the drawings in which likereference characters refer to the same parts throughout the differentviews. The drawings are not necessarily to scale, emphasis instead beingplaced upon illustrating the principles of the invention.

FIG. 1 is a schematic drawing of a servomechanical surgery systemincluding a force-reflecting surgical instrument mounted to apositioning mechanism.

FIG. 2 is a schematic drawing of a positioning mechanism in forward andrearward positions with the surgical instrument inserted into a patient.

FIG. 3 is a perspective view of a force-reflecting surgical instrument.

FIG. 4 is a schematic view of the cable drive actuation of the rotarymotion of the force-reflecting surgical instrument.

FIG. 5 is a perspective view of the distal end of the force-reflectingsurgical instrument.

FIG. 6 is a simplified schematic drawing of the force-reflectingsurgical instrument showing the relationship of the cables and pulleys.

FIG. 7 a is a perspective view of a cable wrapped around the drive shaftof a drive motor.

FIG. 7 b is a schematic drawing showing another preferred method fordriving the cables in the present invention.

FIG. 8 is a top view of the wrist member of another preferredforce-reflecting surgical instrument.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The surgical instrument in the first embodiment includes an elongatesupport member having a proximal portion and a distal portion lyingalong a longitudinal axis. A distal wrist member is rotatably coupled tothe distal portion of the support member by a wrist joint. First andsecond opposed work members are mounted to respective first and seconddriven capstans. The first and second driven capstans are rotatablymounted to the wrist member by respective first and second capstanjoints which preferably have a common axis. First, second, third andfourth intermediate idler pulleys are rotatably mounted to the wristmember about the wrist joint. A cable drive system including first,second, third and fourth cables is provided. Each intermediate idlerpulley is engaged by one cable and each driven capstan is drivinglyengaged by two cables. The cable drive system is capable of pivoting thewrist member about the wrist joint and pivoting the work membersindependently of each other about the capstan joints.

In preferred embodiments, a linear bearing is mounted in slidingengagement with the support member for allowing the distal portion ofthe support member to be reciprocated along the longitudinal axisrelative to the proximal portion of the support member. In suchembodiments the cable drive system is capable of translating the supportmember along the longitudinal axis. In preferred embodiments, thesupport member may also include a rotary joint separating the proximaland distal portions of the support member for allowing rotation of thedistal portion relative to the proximal portion about the longitudinalaxis. In such embodiments the first through fourth cables are capable oftwisting about the longitudinal axis during rotation of the distalportion and the cable drive system comprises a fifth cable coupled tothe rotary joint for rotating the distal portion about the longitudinalaxis.

The present invention also provides a novel system for tensioning thefirst, second, third and fourth cables. A first proximal idler pulleyrotatably engages and tensions the first and second cables. A secondproximal idler pulley rotatably engages and tensions the third andfourth cables. Fifth and sixth cables are connected to the first andsecond proximal idler pulleys for tensioning the first and secondproximal idler pulleys. A third more proximal idler pulley is rotatablymounted to a support member for rotatably engaging and tensioning thefifth and sixth cables.

The surgical instrument further includes a plurality of actuators, eachfor driving one of the cables of the cable drive system. The instrumentpreferably comprises one actuator for each degree-of-freedom of theinstrument. The actuators are preferably servomotors which arepositioned between the intermediate idler pulleys and the proximal idlerpulleys. The servomotors are preferably directly coupled to the cablesby means of a drive capstan mounted on the drive shaft of theservomotor.

The surgical instrument is adapted to be a slave device which iscontrolled by a master device and a controller. Movements of theinstrument and the master device as well as forces exerted thereon maybe scaled between the instrument and the master device. A positioningmechanism having two degrees-of-freedom may be mounted to the instrumentfor positioning the instrument over a work site. The positioningmechanism may provide the instrument with redundant degrees-of-freedomfor positioning the endpoint. The combination of a positioning mechanismwith the applicants articulated surgical instrument is adapted to enablea surgeon operating the master device to feel forces that areexperienced by the instrument during positioning and use of theinstrument with greater sensitivity than with prior systems.

Details about the preferred attributes of the surgical system are alsodescribed in applicants' copending applications titled “Force-ReflectingSurgical Instrument And Positioning Mechanism For Performing MinimallyInvasive Surgery With Enhanced Dexterity And Sensitivity” and “WristMechanism For Surgical Instrument For Performing Minimally InvasiveSurgery With Enhanced Dexterity And Sensitivity” filed on even dateherewith. The disclosures of these applications are incorporated hereinby reference.

Referring to FIG. 1, telesurgery system 10 allows a surgeon at onelocation to perform surgery on a patient at another location. Thesurgeon may be in the same operating room as the patient or many milesaway. Telesurgery system 10 includes a force-reflecting surgicalinstrument 12 which is mounted by a bracket 36 to a positioningmechanism 14. Instrument 12 and positioning mechanism 14 are controlledby a computer 11 and a master device 150 which is manipulated by asurgeon at a remote location. Instrument 12 and positioning mechanism 14are driven by drive motors M1, M2, M3, M4, M5, M6 and M7 (FIGS. 3, 4, 6and 7 a-b) in conjunction with a series of cables and pulleys.

Instrument 12 has low friction, low inertia and high bandwidth but asmall range of motion. Positioning mechanism 14 has a large range ofmotion but typically has a higher inertia and a lower bandwidth than theinstrument. The combination of instrument 12 and positioning mechanism14 in a macro/micro actuation scheme results in a system with increaseddynamic range compared to either of its individual components.Positioning mechanism 14 provides telesurgery system 10 with redundantdegrees-of-freedom and helps positions instrument 12 at a surgicalworksite so that instrument 12 is generally in the proper location forperforming the necessary surgery. Thus, by mounting instrument 12 onpositioning mechanism 14, telesurgery system 10 is provided with highquality force control through the use of instrument 12 while at the sametime having a large range of motion due to positioning mechanism 14.Instrument 12 is mounted on positioning mechanism by means of mountingbracket 36. Preferably, the Instrument 12 is releasably attached topositioning mechanism 14 using any suitable releasable attachment meanssuch as screws, bolts, clamps.

Instrument 12 has a proximal portion 28 a which is rotatably coupled toa distal portion 28 b by a rotary joint 26. Proximal portion 28 a isslidably coupled to a sliding bracket 96 which forms a sliding joint 30.Sliding bracket 96 is fixed to bracket 36. Bracket 36 is a mountingbracket which releasably connects instrument 12 to positioning mechanism14. Distal portion 28 b of instrument 12 includes a wrist member whichis rotatably coupled to a tubular support member 24 by a wrist joint 16.Two opposed work members 20 a and 20 b are fixed to respective drivencapstans 18 a and 18 b which are rotatably coupled to wrist member 22about capstan joints 19 a and 19 b. The work members 20 a and 20 b canbe the operative end of standard surgical instruments such as scissors,retractors, needle drivers and electrocautery instruments.

Instrument 12 has five degrees-of-freedom with sliding joint 30providing linear motion along longitudinal axis C-C, rotary joint 26providing rotational motion about axis C-C, wrist joint 16 providingrotational motion about axis B-B and capstan joints 19 a and 19 bproviding rotational motion about axis A-A for work members 20 a and 20b. Instrument 12 provides master device 150 with four degrees of forcereflection so that the surgeon can have tactile feedback of surgicalprocedures. These degrees of force reflection include x, y and z forcesexerted on the work members 20 a and 20 b, as well as the holding forcebetween work members 20 a and 20 b. However, force reflection can beprovided on more or fewer motion axes as required in any particularembodiment.

Positioning mechanism 14 is a two degree-of-freedom linkage which ispreferably a four bar linkage which rotates about an axis E-E.Positioning mechanism 14 has a series of rigid members 36, 40, 42, 60and 62 which are joined together by joints 34, 38, 48, 50, 52, 54, 56.Positioning mechanism 14 also includes a base 68 having ears 58 whichengage shafts 64 and 66 to form a joint 57 for pivoting about axis E-E.Joint 56 allows link 62 to rotate about axis D-D which is orthogonal toaxis E-E. The four bar linkage of rigid members 36, 40, 42, 60 and 62transmits this rotation to instrument 12 via bracket 36 causinginstrument 12 to rotate about axis E-E and axis D′-D′ (axis D′-D′ isparallel to axis D-D and intersects axis E-E orthogonally). Thus thefour bar linkage operates to move point P.sub.s of instrument 12 aboutthe surface of a sphere having its center at a remote center 111.Although a four bar linkage has been shown, the articulated surgicalinstrument of the present invention can be supported by any suitablepositioning mechanism. To be suitable for minimally invasive surgery thepositioning mechanism must pivot the surgical instrument about axes thatintersect at the orifice through which the instrument is inserted intothe patient.

Haptic master device 150 suitable to control instrument 12 is a sevendegree-of-freedom input device. During use the master 150 is fixed inplace to a console or cart or similar stationary support such that themount provides a fixed reference point. During use, the surgeonmanipulates the position and orientation of the master mechanismrelative to its stationary support. Linkages, motors and encoders of themaster detect the surgeon's movements and transmit them to the computer.The motors of the master preferably also provide force feedback to thesurgeon. This controls motions of instrument 12 and positioningmechanism 14 and thus controls the position of the distal end ofinstrument 12 relative to the surgical site.

One apparatus suitable for use as a master in the presently describedsystem is described in U.S. Pat. No. 5,587,937, titled Force ReflectingHaptic Interface the contents of which are incorporated by referenceherein. Another suitable master device is described in U.S. Pat. No.5,576,727, titled Electromechanical Human-Computer Interface WithForce-Feedback the contents of which are incorporated by referenceherein. The haptic master apparatus disclosed in the above referenceswould require the addition of a further powered degree-of-freedom toprovide force reflection from gripping the work members. For example,finger grippers may be attached to a motor and encoder on a separatemechanism for operation by the other hand of the surgeon. Alternatively,finger grippers may be attached to a motor and encoder on the samedevice for operation by the surgeon.

When employing telesurgery system 10 for laparoscopic surgery,positioning mechanism 14 is mounted to a manually-operated setup joint(not shown). After the setup joint has been used to position the tooland lock the tool in place, the surgeon then manipulates master device150 to move instrument 12 through a cannula 113 inserted through smallincision 112 in the abdominal wall 110 of the patient. In response tomanipulation of master device 150, the distal portion 28 b of theinstrument 12 is translated downwardly relative to positioning mechanism14 along sliding joint 30 for insertion through cannula 113 andabdominal wall 110.

Once within the abdomen, the distal portion 28 b of instrument 12 isfurther positioned over the desired surgical site. FIG. 2 depicts motionof mechanism 14 pivoted about axis D-D in forward and rearward positionsfor making large position movements. Positioning mechanism 14 pivotsabout axes D-D and E-E to perform large movements of telesurgery system10 while precise movements are made by the joints of instrument 12.Point 111 on instrument 12 is a remote point of rotation frompositioning mechanism 14 which coincides with entry wound 112. Whenpositioning mechanism 14 is pivoted about axes D and E, instrument 12pivots about point 111. Note that point 111 adjacent incision 112remains stationary as the instrument 12 is pivoted within the patient.As a result, incision 112 only needs to be large enough to acceptinstrument 12.

As positioning mechanism 14 pivots, if wrist member 22 or work members20 a/20 b engage tissue causing rotation about joints 16 or 19 a/19 b,instrument 12 will reorient itself so that instrument 12 is maintainedrelative to positioning mechanism 14 in the middle of its workspace. Ifnecessary, positioning mechanism 14 can slow down as instrument 12 isreorienting itself.

Once instrument 12 is in the proper position, by further manipulatingmaster device 150, the surgeon can perform the necessary surgicalprocedures on the patient with instrument 12. Forces experienced byinstrument 12 are reflected back to the surgeon by master device 150.The reflected forces may be scaled up in order to allow the surgeon tobetter “feel” the surgical procedures. As a result, the surgeon can feelinstrument 12 engaging types of tissue that do not provide muchresistance. In addition, movements of master device 150 relative toinstrument 12 may be scaled down so that the precision and dexterity ofinstrument 12 can be increased.

Positioning mechanism 14, because it is optimized to have a large rangeof motion, is likely to have higher inertia, higher friction and lowerresolution than instrument 12. Moreover, friction forces in cannula 113and disturbance forces at incision 112 may be applied to the positioningmechanism.

However, in applicants' preferred embodiment, primarily the surgicalinstrument detects forces for force reflection. Therefore, the higherinertia and friction of the positioning mechanism and the extraneousforces acting on it are excluded from the force reflection system. Thus,the quality of the force reflection between the tip of the instrument 12and the master device is greatly improved.

Referring to FIGS. 3, 4 and 5, instrument 12 is now described in greaterdetail. Tubular support member 24 of distal portion lies along axis C-Cand houses a series of cables C1, C2, C3 and C4 which travel the lengthof tubular support member 24. Cables C1, C2, C3 and C4 control therotation of joints 19 a, 19 b and 16 for controlling the operation ofwork members 20 a and 20 b and the orientation of wrist member 22. Wristmember 22 includes two opposed distal ears 21 a and 21 b forming aclevis for supporting driven capstans 18 a and 18 b at respectivecapstan joints 19 a and 19 b which lie along axis A-A. Wrist member 22also includes two opposed proximal ears 23 a and 23 b forming a clevisfor supporting intermediate idler pulleys 70 and 72 which lie along axisB-B between ear 23 a and tongue 24 a at wrist joint 16. Intermediateidler pulleys 74 and 76 are supported between ear 23 b and tongue 24 a.Cables C1, C2, C3 and C4 engage driven capstans 18 a/18 b as well asintermediate idler pulleys 70, 72, 74 and 76 as described later ingreater detail.

Work members 20 a and 20 b may be removably fixed to respective drivencapstans 18 a and 18 b. Although work members 20 a and 20 b are depictedin the figures as being grippers, work members 20 a and 20 b can bereplaced with other types of work members such as scissors, cutters,graspers, forceps or needle holders for stitching sutures. Typically,the work members are fixed to driven capstans 18 a and 18 b by a screw,clip or other suitable fastener. However, the work members may also bepermanently affixed to the driven capstans by soldering or welding orthe like or may be formed in one piece with the driven capstans.

Work members 20 a and 20 b together comprise one form of surgical endeffector. Other surgical end effectors may be used in the surgicalinstrument of the present invention. End effectors simply may comprisestandard surgical or endoscopic instruments with their handles removedincluding, for example, retractors, electrocautery instruments,microforceps, microneedle holders, dissecting scissors, blades,irrigators, and sutures. The end effectors will typically comprise oneor two work members.

Proximal portion 28 a of instrument 12 includes support brackets 98 and102 which are connected together by a support rod 100 as well as twoguide rails 104 and 106. A rotary bearing 91 forming rotary joint 26 ishoused within support bracket 98 for supporting tubular support member24. Sliding bracket 96 is slidably mounted to guide rails 104 and 106along linear bearings. As shown in FIG. 1, sliding bracket 96 isconnected by bracket 36 to positioning mechanism 14. Sliding bracket 96preferably has about 8 inches of travel for surgical applications.

Drive motors M1, M2, M3, M4 and M5 are mounted to sliding bracket 96 anddrive respective cables C1 C2, C3 and C4 and C5. Sliding bracket 96supports each of the drive motors. During operation sliding bracket 96is connected to positioning mechanism 14 by mounting bracket 36. Wheninstrument 12 is mounted on positioning mechanism 14, the drive motorsoperate to move distal portion 28 b relative to sliding bracket 96.Sliding bracket 96 thus forms the support bracket of the surgicalinstrument. Each drive motor M1, M2, M3, M4 and M5 includes a respectiveencoder E1, E2, E3, E4 and E5 for providing computer 11 with therotational position of their respective drive shafts.

As shown in FIG. 4, drive motor M5 has a drive shaft capstan 93 whichengages a cable drive loop consisting of Cable C5. The cable passesaround rear tensioning pulley 83. The cable passes around idler pulleys84 and 85 and around drive capstan 90 which forms the proximal end oftubular support member 24. Thus rotation of actuation of motor M5 can beused to rotate tubular support member 24 and the end effector itsupports.

Referring to FIG. 6, the cable drive system of instrument 12 is nowdescribed in greater detail. Work members 20 a and 20 b, wrist member 22and the translation of instrument 12 along longitudinal axis C-C aredriven by cables C1, C2, C3 and C4 which are arranged in an N+1actuation scheme. The N+1 actuation scheme allows the actuation of athree degree-of-freedom wrist using four cables. Four cables is thetheoretical minimum possible number of tension elements required todrive three degrees-of-freedom and thus allows the instrument to be ofminimum size and weight. Alternative actuation schemes using more cablesmay be desirable in situations where the forces required for actuationof different motions differ greatly in magnitude. The disadvantage ofusing more cables is an increase in weight, complexity and minimum size.

In FIG. 6, the rotational motion of joint 26 about axis C-C is omittedin order to more easily show cables C1-C4. Such rotation results only intwisting of the cables C1-C4 between motors M1-M4 and pulleys 70, 72, 74and 76. The cables are however arranged in tubular support member 24such that this twisting does not significantly change the length of thecable path. Care should however be taken to prevent over-rotation of theinstrument which would cause the cables to twist into contact with eachother and create friction between the cables.

As shown in FIG. 6, cables C1 and C2 form two sides of a continuouscable loop 44. Cable C1 of loop 44 engages a proximal idler pulley 80,the drive shaft of motor M1, intermediate idler pulley 70 and drivencapstan 28 a. Cable loop 44 returns from driven capstan 18 a as cable C2and engages intermediate idler pulley 76, the drive shaft of motor M2and proximal idler pulley 80.

As shown in FIG. 6, cables C3 and C4 form two sides of a continuous loopof cable 46. Cable C3 of cable loop 46 engages proximal idler pulley 78,the drive shaft of motor M3, intermediate idler pulley 72 and drivencapstan 18 b. Cable loop 46 returns from driven capstan 18 b as cable C4and engages intermediate idler pulley 74, the drive shaft of motor M4and proximal idler pulley 78.

As shown in FIG. 6, proximal idler pulleys 78 and 80 are tensioned bycables C7 and C6 which are fixed to the center of proximal idler pulleys78 and 80. Cables C7 and C6 form two sides of a single cable 45 whichengages proximal idler pulley 82 which is rotatably mounted to supportbracket 102 by shaft 82 a. Shaft 82 a is preferably movably mounted tosupport bracket 102 by a mechanism such as a lead screw. The lead screwmay then be adjusted to appropriately tension cables C7 and C6. Thetension is also applied via idler pulleys 78 and 80 to cables C1, C2, C3and C4. A similar lead screw tensioning scheme can be used to tensioncable C5 by longitudinal movement of idler pulley 83. It may be requiredfor idler pulleys 82 and 83 to be mounted on separately adjustableshafts for these purpose instead of single shaft 82 a illustrated inFIG. 3.

Driven capstans 18 a and 18 b may have different diameters in order toallow cables C1 through C4 to suitably engage their respectiveintermediate idler pulleys. Cables C1 and C2 engage the outerintermediate idler pulleys 70 and 76 while cables C3 and C4 engage theinner intermediate idler pulleys 72 and 74. Proximal idler pulleys 78and 80 are sized such that pulley 80 is larger than pulley 78 to keepthe cables straight.

Drive motors M1, M2, M3 and M4 control rotation of wrist member 22 aboutaxis B-B, translation of instrument 12 longitudinally along axis C-C androtation of work members 22 a and 22 b independent of each other aboutaxis A-A by driving cables C1, C2, C3 and C4. Drive motors M1 and M2drive cables C1/C2 in unison in opposition to cables C3/C4 driven bydrive motors M3 and M4 in order to rotate wrist member 22 about axisB-B. Drive motor M1 drives cable C1 in opposition to cable C2 driven bydrive motor M2 to rotate capstan 18 a and attached work member 20 aabout axis A-A. In addition, drive motor M3 drives cable C3 inopposition to cable C4 driven by drive motor M4 to rotate capstan 18 band attached work member 20 b about axis A-A. All four drive motors M1,M2, M3 and M4 drive cables C1, C2, C3 and C4 simultaneously to translateinstrument 12 along longitudinal axis C-C.

Locating drive motors M1, M2, M3, M4 and M5 on sliding bracket 96 makesthe distal portion 28 b of instrument 12 have a small moving mass sincethe motors themselves remain stationary during actuation of theinstrument. Although the motors are moved by positioning mechanism 14,the weight and inertia of the motors do not affect force reflection.This is because, as stated above, in the preferred embodiment, only theinstrument is used to reflect forces to the master. In addition,employing cables instead of gears to control instrument 12 minimizes theamount of friction and backlash within instrument 12. The combination ofsmall moving masses and low friction enables instrument 12 to provideforce reflection to master device 150 with high sensitivity.

Certain possible changes to the configuration of pulleys, cables andmotors described above will be apparent to those of skill in the art.Although cables C1/C2, C3/C4, C5 and C7/C6 have been depicted to besides of the same cables, cables C1-C7 alternatively can each beindividual cables which are fixed to driven capstans 18 a and 18 b, andproximal idler pulleys 78, 80 and 82. Moreover, although drive motorsM1, M2, M3 and M4 have been depicted to drive cables C1, C2, C3 and C4respectively, alternatively, some drive motors can be relocated fromcables C1-C4 onto cables C7 and C6 for driving cables C7 and C6. Thechoice of the particular drive scheme employed in a particularembodiment will depend on the constraints of the forces required to beexerted by the instrument and the need to reduce the inertia andfriction of the parts of the instrument that move during its actuation.

The surgical instrument of the present invention has been illustrated asusing drive motors M1, M2, M3, M4 and M5. This drive motors may bestandard servo motors having position encoders as shown in FIG. 3.However, other actuators may be used, such as hydraulic actuators andpiezoelectric motors. To be used as an actuator in the present surgicalinstrument a drive mechanism should be able to provide variable andcontrollable force and position control.

Cables C1, C2, C3, C4, C7, C8 and C9 are driven by being wrapped aboutthe drive shaft of their respective drive motors M1, M2, M3, M4, M5, M6and M7. This cable drive method and an alternative cable drive methodare illustrated in more detail in FIGS. 7 a and 7 b. For example, inFIG. 7 a, cable C4 of cable loop 46 is wrapped around the drive shaft ofmotor M4. Cable C4 is preferably wrapped two times around the driveshaft to provide enough friction between the cable C4 and the driveshaft to prevent slippage. In order to further prevent slippage thecable may be fixed to the drive shaft at one point by soldering, weldingor mechanical fixing means. However, in such an embodiment the range ofmotion of the cable is limited by the length of cable wrapped around thedrive shaft or capstan thus several turns of cable are usually required.

FIG. 7 b depicts another preferred method for driving cables. Forexample, motor M4 includes a drive wheel 43 a and a idler wheel 43 b forfrictionally driving an elongate member 47 therebetween. Cable C4consists of two halves, 46 a and 46 b which are fixed to opposite endsof member 47.

FIG. 8 depicts the distal end and wrist member 116 of another preferredinstrument 117. Instrument 117 differs from instrument 12 in thatinstrument 117 includes eight intermediate idler pulleys instead offour. Instrument 117 includes intermediate idler pulleys 76, 74, 72 and70 at wrist joint 16 but also includes intermediate idler pulleys 76 a,74 a, 72 a and 70 a which are positioned adjacent to idler pulleys 76,74, 72 and 70 on tongue 24 a along shaft 118. Cables C1, C2, C3 and C4do not make a complete wrap around each intermediate idler pulley butinstead contacts a variable amount of the of the surface of each pulleyvarying in a range between 0.degree. and 180.degree. over the range ofmotion of the wrist about axis 16. This prevents the cables fromcrossing each other and rubbing together which prevents friction andnoise.

Although the present invention has been described for performinglaparoscopic surgery, it may also be used for other forms of endoscopicsurgery as well as open surgery. The present manipulator could also beemployed for any suitable remote controlled application requiring adexterous manipulator with high quality force feedback. Moreover, whilethis invention has been particularly shown and described with referencesto preferred embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the appended claims.

1. An articulated surgical instrument for minimally invasive surgerycomprising: a sliding bracket slidably coupled to a support bracket; anelongate support member having a proximal end coupled to the slidingbracket, and a distal end insertable into the body of a patient duringminimally invasive surgery, the support member being movable along itslongitudinal axis by sliding the sliding bracket relative to the supportbracket: a wrist member coupled to the distal end of the elongatesupport member, the wrist member rotatable relative to the elongatesupport member about a first axis; a surgical end effector coupled tothe wrist member, the surgical end effector comprising a first workmember rotatable relative to the wrist member about a second axis; andactuators disposed at the sliding bracket, the actuators coupled to thewrist member by cables to rotate the wrist member about the first axis,the actuators further coupled to the first work member by cables torotate the first work member about the second axis; the actuatorscomprising four actuators, the four actuators coupled by four cables tofour pulleys coupled to the wrist member, wherein selective actuation ofthe four actuators rotates the wrist member about the first axis andtranslates the sliding bracket relative to the support bracket along alongitudinal axis of the support member.
 2. The instrument of claim 1,at least two of the four actuators further coupled to a pulley attachedto the first work member, wherein selective actuation of the at leasttwo of the four actuators rotates the first work member about the secondaxis.
 3. The instrument of claim 2, the surgical end effector furthercomprising a second work member, the second end effector coupled to atleast two of the four actuators not coupled to the pulley attached tothe first work member, wherein selection of the at least two of the fouractuators not coupled to the first work member rotates the second workmember about the second axis.
 4. The instrument of claim 3, wherein afirst actuator drives a first cable in opposition to a second cabledriven by a second actuator to move the first work member with a firstdegree-of-freedom relative to the support member.
 5. The instrument ofclaim 4, wherein a third actuator drives a third cable in opposition toa fourth cable driven by a fourth actuator to move the second workmember relative to the first work member with one degree-of-freedom. 6.The instrument of claim 5 wherein the first and second actuators drivethe respective first and second cables in unison in opposition to thethird and fourth cables driven in unison by the respective third andfourth actuators in order to move the first work member relative to thesupport member with a second degree-of-freedom.
 7. The instrument ofclaim 5 wherein the first, second, third and fourth actuators driverespective first, second, third and fourth cables in unison in order tomove the elongate support member along the longitudinal axis.
 8. Theinstrument of claim 1, wherein said actuators are controllable byelectrical signals to selectively drive the wrist member and thesurgical end effector.
 9. The instrument of claim 8, wherein saidelectrical signals are derived from a master controller, whereinmovement of said master controller in first and second degrees offreedom generate said electrical signals.
 10. The instrument of claim 9,wherein movement of said master controller in said first degree offreedom relative to a stationary point causes movement in the samedirection of said the wrist member relative to a surgical site.
 11. Theinstrument of claim 10, wherein movement of said master controller insaid second degree of freedom relative to said stationary point causesmovement in the same direction of the surgical end effector relative tosaid surgical site.
 12. The instrument of claim 1, the first axis beingperpendicular to the second axis.
 13. The instrument of claim 1, thesupport member having a longitudinal axis running between the proximalend and the distal end, the instrument further comprising an auxiliaryactuator coupled to the proximal end of the elongate support member byan auxiliary cable, the auxiliary actuator disposed on the slidingbracket, the auxiliary actuator rotating the support member about itslongitudinal axis relative to the sliding bracket by pulling theauxiliary cable.
 14. The instrument of claim 1, further comprising amounting bracket coupled to the sliding bracket, the mounting bracketadapted to releasably connect the articulated surgical instrument to apositioning mechanism.
 15. The instrument of claim 14, the positioningmechanism comprising a remote centering mechanism for pivoting saidinstrument about a minimally invasive surgical entry point.
 16. Theinstrument of claim 1, wherein said plurality of actuators iscontrollable by electrical signals to selectively drive the wrist memberand the surgical end effector.
 17. The instrument of claim 16, whereinsaid electrical signals are derived from a master controller, whereinmovement of said master controller in first and second degrees offreedom generate said electrical signals.
 18. The instrument of claim17, wherein movement of said master controller in said first degree offreedom relative to a stationary point causes movement in the samedirection of said the wrist member relative to a surgical site.
 19. Theinstrument of claim 18, wherein movement of said master controller insaid second degree of freedom relative to said stationary point causesmovement in the same direction of the surgical end effector relative tosaid surgical site.
 20. A surgical instrument comprising: a slidingbracket slidably coupled to a support bracket; an elongate supportmember having a proximal end coupled to the sliding bracket, and adistal end insertable into the body of a patient during minimallyinvasive surgery, the support member being movable along itslongitudinal axis by sliding the sliding bracket relative to the supportbracket; a wrist member coupled to the distal end of the elongatesupport member, the wrist member rotatable relative to the elongatesupport member about a first axis; a surgical end effector coupled tothe wrist member, the surgical end effector comprising a first workmember rotatable relative to the wrist member about a second axis;pulley means disposed at the wrist member for moving the wrist memberand the surgical end effector; and actuation means disposed at thesliding bracket for selectively actuating the pulley means; theactuation means comprising four actuators, the four actuators coupled byfour cables to four pulleys coupled to the wrist member, whereinselective actuation of the four actuators rotates the wrist member aboutthe first axis and translates the sliding bracket relative to thesupport bracket along a longitudinal axis of the support member.
 21. Amethod of actuating a surgical instrument, the surgical instrumentcomprising a sliding bracket slidably coupled to a support bracket, theinstrument further comprising an elongate support member having aproximal end coupled to the sliding bracket and a distal end insertedinto the body of a patient during minimally invasive surgery, a wristmember coupled to the distal end of the elongate support member, and asurgical end effector coupled to the wrist member, the surgical endeffector comprising a first work member, the method comprising: movingthe support member along its longitudinal axis by sliding the slidingbracket relative to the support bracket; selectively actuating aplurality of actuators disposed at the sliding bracket, the actuatorscomprising four actuators, the four actuators coupled by four cables tofour pulleys coupled to the wrist member, wherein selective actuation ofthe four actuators rotates the wrist member about the first axis andtranslates the sliding bracket relative to the support bracket along alongitudinal axis of the support member; rotating the wrist memberrelative to the elongate support member about a first axis in responseto said selective actuation; and rotating the first work member relativeto the wrist member about a second axis in response to said selectiveactuation.